The present invention generally relates to a rotary engine and, more particularly, to a rotary engine that improves output efficiency, reduces friction wear, and decreases fuel consumption, and at the same time is easy to manufacture and has the flexibility to increase the number of cylinders to improve the performance of the rotary engine.
FIG. 23 shows a conventional reciprocating engine 100 that uses a confined space for sequentially performing the four cycles of intake, compression, combustion, and exhaust, where the crank 110 inside the engine 100 generates the rotational output. The theory behind the traditional engine 100 has been widely applied in our daily lives for all kinds of land, sea, and air transportation, as well as power generating apparatus for agricultural, manufacturing, and military use. Even though the reciprocating engine is broadly accepted and used, it does not mean that the performance has reached perfection. In fact, there are the following bottlenecks in the reciprocating engine 100 regardless whether it is of 2-stroke or 4-stroke design:
(1) Output power cannot be easily increased: reciprocating engine 100 relies on a crank 110 to convert the reciprocating motion of the piston 120 into a rotational motion which is then coupled to an external driving system. The conversion from the reciprocating motion into the rotational motion causes a loss in the output efficiency, which is unavoidable due to structural limitations.
(2) Structure and manufacturing are complex: the output efficiency of the reciprocating engine 100 is highly related to the precision in the manufacture of the crank 110, wherein the precision of the crankshaft 112 and the crank pin 115 needs to be extremely high. If there is any error in the level of precision, the conversion from reciprocating output to rotational output will be greatly decreased. Moreover, in a four-cylinder reciprocating engine, the internal parts add up to forty linked parts for operation which results in a high manufacturing cost.
(3) Torque-increase causes fuel consumption to increase: a reciprocating engine 100 can increase the stroke, that is to increase the distance between the connecting rod 117 and the crank 110, to rise torque. If the stroke is increased, the bore of the cylinder 125 also needs to be increased; therefore, fuel consumption is greatly increased, so an increase in torque and a decrease in fuel consumption cannot be achieved simultaneously.
(4) Increase of the number of cylinders is limited: if the number of cylinders is increased to raise the horsepower of the reciprocating engine 100, the engine overall size is unavoidably increased. Regardless of the configuration of the cylinders, such as straight, boxer, and slant or the type of configuration V, W, and H, the engine size always increases significantly when cylinders are added.
(5) high-rpm causes wear: when the reciprocating engine 100 revolves over 2000 rpm, such high-rpm reciprocating action will cause the piston 120 to experience an extremely high amount of wear, which, at the same time generates a lot of heat, increasing damage to parts and decreasing the lifespan of the engine. As a result, fuel consumption of the engine increases over time.
In order to solve problem (1) of reciprocating engine 100 regarding power output, a German engineer Felix Wankel invented the Wankel rotary engine 150, which is illustrated in FIG. 24. An arciform triangular rotor 160 is held within a rotor holding bore 165, which replaces the cylinder 125 and the piston 120 of the reciprocating engine 100. The conformance to a peri-trochoidal profile is driven by the requirement that all three bearing points of the Wankel rotor remain in constant contact with the inner surface of the engine. The rotor rotates in a planetary motion through the engaging of a rotor gear on the rotor with a gear on an output shaft. The interplay of the arciform triangular rotor within the rotor holding bore creates three chambers therein. Under planetary motion of the rotor, the chambers outside of the rotor vary their capacities to perform the four cycles of intake (suction), compression, combustion (expansion), and exhaust. The output of the Wankel engine 150 is directly connected to the arciform triangular rotor 160 without the need of motion type conversion. The output of the Wankel engine 150 is twice that of the reciprocating engine 100, and the overall number of components of the Wankel engine 150 is greatly reduced; therefore, from the market launch in 1958, it caused a great shock in the industry. In the era of the 60s, when power was most sought after, the high output rotary engine was put on sports cars, breaking speed records for sports cars, and the rotary engine seemed poised to take over the traditional reciprocating engine 100.
Although the Wankel engine 150 improved problem (1) of the reciprocating engine 100, it failed to successfully solve problems (2), (3), and (4). Furthermore, the path of the arciform triangular rotor 160 is not smooth, so at high-rpm, wear at the tips of the rotor 160 causes the exhaust cavity immediately following the ignition point to rapidly enlarge. This causes a significant portion of the gas pressure to be lost to expansion within the enlarging cavity, instead of being converted into useable torque. The problem of power decreasing and fuel consumption increasing becomes more significant as the engine runs more, and, for about every 30,000 miles, the engine needs rebuilding or replacement. This disadvantage proved fatal for the the Wankel engine 150, resulting in the higher carbon monoxide exhaust levels and fuel consumption. The architecture of the Wankel engine, i.e., a peri-trochoidal section, makes it difficult to improve the combustibility of the combustion phase to decrease the exhaust quantity of unburned gases. Although the number of parts of the Wankel engine 150 is much less than a conventional engine, the precision of the inner gear 180 and the outer gear 185 of the arciform triangular rotor 160 has to be extremely high, offsetting the cost-savings generally associated with having fewer parts. Furthermore, the arciform triangular rotor 160 is the part that undergoes the most wear in the engine, and, if there is a problem on a Wankel engine 150, the whole unit is usually replaced, which reduces practicality. The Wankel engine 150 overcomes some of the limitations of the reciprocating engine 100, but possesses other disadvantages not found in generic reciprocating engines; therefore, market acceptance has not been as rapid as expected.
Beginning with the energy shortage of 1973, vehicle engine research has shifted focus from increasing power to the twin goals of decreasing exhaust emissions and fuel consumption. The shortcomings of the Wankel engine rapidly became apparent and most of the car manufacturers cancelled development of the Wankel engine and returned to designs employing the reciprocating engines. Among all the car manufacturers, only Mazda continued the use of Wankel engine and kept making performance modifications. Mazda launched the RX7 model in 1999 with the use of modern lubricants and ceramic material for the triangular tips to lower the wearing problem of the Wankel engine. However, the use of this material greatly increases the manufacturing cost.
Any novel industrial product must possess advantages and performance that are not found in prior art. Moreover, the setup of the production equipment and production line cannot be too expensive compared to prior art, otherwise existing manufacturers will not the existing product line and business prospects. Possession solely of technical performance is generally not enough for a new design to change the percentage of market share away from conventional technology. Performance has to be combined with ease of manufacturing and low cost to attract manufacturers to invest in or replace production lines.
On inspection of the history of the Wankel engine, it can be seen that the difficulty of manufacturing the arciform triangular rotor and the requirement for entirely new equipment to manufacture such a rotary engine caused the Wankel engine to fail to attract manufacturers.
Summarizing the above, new designs tend to introduce new problems; therefore, advantages must significantly out-weigh disadvantages in order for the new design to take hold. The focus of current engine research is how to design a simple and low cost engine which has higher output than the conventional reciprocating engine while at the same time lowers wear and fuel consumption, increases torque without the expense of fuel consumption, and does not increase engine size significantly with the addition of cylinders.
An objective of the present invention is to provide a high output rotary engine.
Another objective of the present invention is to provide a rotary engine that is simple yet low-cost to manufacture.
Another objective of the present invention is to provide a rotary engine that does not increase fuel consumption while increasing the torque of the rotary engine.
Another objective of the present invention is to provide a rotary engine that does not increase engine size while increasing the number of cylinders of the rotary engine.
Another objective of the present invention is to provide a rotary engine that minimizes wear while rotating.
Another objective of the present invention is to provide a rotary engine that decreases fuel consumption.
Another objective of the present invention is to provide a rotary engine that provides good lubrication without requiring additional lubrication equipment.
Another objective of the present invention is to provide a rotary engine that is efficiently air-cooled.
Another objective of the present invention is to provide a rotary engine that has smooth rotation over a long lifespan.
In achieving the above and other objectives, the rotary engine of the present invention comprises: a stationary cylinder wherein the surface has an intake aperture, exhaust aperture, and ignition aperture (for providing combustion); a cover plate having an elliptical track which is coupled to the stationary cylinder to form a first cavity; a driving disk that is mounted on a first shaft in the middle of the stationary cylinder by method of insertion, such that driving disk is accommodated inside the first cavity, and, at the same time, the first shaft protrudes out of the stationary cylinder for coupling to a driving source which provides drive for the driving disk; and, at least a rotational cylinder having a second cavity therein placed on the surface of the driving disk and driven by the driving disk that is mounted to the first shaft within the first cavity. The surface of the rotational cylinder comprises a window interacting with the intake aperture, the exhaust aperture, and the ignition aperture during rotation of the rotational cylinder. The intake aperture, the exhaust aperture, and the ignition aperture perform both the intake/exhaust process and the combustion process between the second cavity and the outside through the intake/exhaust window while the two rotational cylinders are rotating; at least one swing piston corresponding to the rotational cylinder is secured on a second shaft by method of insertion. The swing piston is placed in the second cavity of the rotational cylinder. The second shaft makes a slight rotation that allows the swing piston to swing within the second cavity to render the second cavity as a volume-variable intake/exhaust space; at least one driving member that corresponds to the rotational cylinder couples to the corresponding second shaft and is used to drive the second shaft to rotate within the second cavity, wherein the swing piston swings to alter the volume of the intake/exhaust space. The alteration of the intake/exhaust volume completes the intake, compression, combustion, and exhaust process of this rotary engine design when the rotational cylinder rotates according to the intake, exhaust and ignition sequence.
The aforementioned driving member is a driving wheel assembly comprising a mutually coupled driven wheel set and a leading wheel set, wherein the driven wheel set is coupled to the second shaft that extends out of the driving disk. The driven wheel set is driven by the driving disk to concentrically rotate about the first shaft and the leading wheel set rotates in an elliptical track on the surface of the cover plate. The interconnected rotation between the leading wheel set and the driven wheel set creates a drag that causes the second shaft that is secured by the driven wheel set to rotate slightly and causes the swing piston to swing. The swing piston causes the volume of the intake/exhaust space of the rotational cylinder to gradually increase before the intake operation, to gradually decrease before the ignition operation, to gradually increase again before the exhaust operation, and then gradually decrease to exhaust all gas. This cycle completes the intake, compression, combustion, and exhaust sequence. Furthermore, the rotational cylinder and outer wall of the swing piston are provided with a plurality of seal guides to prevent the rotational cylinder from leaking air through the gap between the rotational cylinder and the swing piston during the intake/exhaust operation.
The rotary engine of the present invention is further coupled to a lubrication oil tank for pumping lubricating oil to flow on the surface of the trenches which exist on the first shaft. During rotation of the first shaft, centrifugal force will automatically spray the lubricating oil onto the surface of the stationary cylinder to cool and lubricate the internal parts of the rotary engine.
In summary, the driving disk, the rotational cylinder, the swing piston, and the driving system of the present invention can solve most of the problems experienced by rotary engines in the prior art. Besides improving the output efficiency of the rotary engine, the number of parts is reduced and the complexity of manufacturing and structure is reduced. A special feature of the present invention is the use of a stationary cylinder and rotational cylinder. This special feature allows flexibly increasing the number of cylinders to increase horsepower without increasing the size of engine or sacrificing fuel consumption. Furthermore, the driving disk and rotational cylinder combination and the design of the leading wheel set of the driving system of the present invention provides smooth operation and low wear at high rpm, which increases the lifespan of the engine and also reduces fuel consumption. The design of the seal guides and lubricating oil device provides the present invention with sealing, cooling, and lubricating.